Hello,

Do you have any of these conditions - mainly reservations affecting the quantity?  One field is the total after transactions, while the other is the amount that is available.  They can and will be different depending on other factors against the inventory part.  This explanation is from the help on the field itself.

Total Available Qty:
This is the total available quantity for this part at this site expressed in inventory unit of measure. The quantity usable minus the quantity reserved; i.e. the non-reserved quantity of the part in stock (location types: picking, floor stock, production line, pallet, pallet deep, pallet buffer, pallet delivery and shipment), including the parts in consignment, regardless of the W/D/R number or the part revision. The parts included are nettable and have not passed their expiration date. Parts with ownership type Customer Owned and Supplier Loaned are excluded. Note however, that the entire quantity may not be available for reservation. This is because quantity in location types Floor Stock or Production Line is also included in the grand total of the available quantity but cannot be reserved by demands that are not from manufacturing.
 

Turns out that somebody in the past had manually delete some rows in inventory_part_in_stock_tab. Then it got out of sync with the inventory transactions. Self-inflicted wound..